1) Arabic uses vowel marks called tashkeel to distinguish between long and short vowels in words. Tashkeel include fat-ha, dhamma, kasra, and sukoon marks above or below letters.
2) Fat-ha is a short slant above a letter indicating a short "a" sound. Dhamma is a small waw above a letter for a short "u" sound. Kasra is a short slant below a letter for a short "i" sound. Sukoon is a small circle above a letter where no sound follows.
3) The hamza represents a pronunciation of "u" when it appears in a word, dividing it into two